Geophysical Habitat of Subglacial Thwaites

Project Overview

Title: Geophysical Habitat of Subglacial Thwaites (GHOST), NSF-NERC Strategic Initiative ‘The International Thwaites Glacier Collaboration (ITGC)’, (2018-24)

The main ITGC website site (see link below) describes the main aim of our GHOST project as: ‘Projecting the retreat rate of Thwaites Glacier, and whether it can stabilize without completely deglaciating the marine basins of West Antarctica to raise global sea level more than 3 m, are of critical importance in a warming world. The objectives of the proposed research are to learn whether basal conditions allow for rapid retreat of the Thwaites Glacier grounding line or whether retreat may slow or stop on the transverse ridge about 70 km inland, and to learn whether englacial and subglacial conditions allow for Thwaites Glacier to rapidly expand its boundaries and deglaciate adjacent marine basins. These objectives will be achieved by using dedicated ice-flow modeling to guide targeted field surveys and experiments over two seasons, to measure the most important unknown quantities and incorporate them into the models.’

As part of this our sub-project will conduct magnetotelluric (MT) geophysical surveys in the 2020-21 and 2021-22 austral summers along a 400 km long transect along and across the flow of the glacier, to characterise the heat flow from the earth’s upper crust into the base of the ice and the substrate beneath. Although this heat flow is poorly constrained by measurements, it is mooted to be elevated beneath the Thwaites Glacier based on indirect evidence. If confirmed by our MT measurements then such heat flow would ensure a ‘warm’ and therefore highly mobile ice base. Geomagnetic field fluctuations induce ‘telluric’ currents in ice sheets and the underlying crust, and MT is a passive electromagnetic (EM) geophysical technique that measures the accompanying electrical voltages at the surface. The data are then used (inverted) to produce diagnostic images of bulk electrical resistivity, which contain the required heat flow information.